Secondary battery and method for manufacturing the same

Abstract

Embodiments relate to a secondary battery, in which an unnecessary space in a case is reduced to increase energy density, and a method for manufacturing the same. A secondary battery includes an electrode assembly provided with a first electrode plate and a second electrode plate, and a case accommodating the electrode assembly. The case includes a first case having a recess, in which the electrode assembly is accommodated, at a central area thereof, wherein the first case has one surface opened, and a second case configured to seal the one opened surface of the first case. The first case further includes an extension part extending from one end of the recess and coupled to the second case, and a round part between the recess and the extension part. A curvature radius of the round part is equal to or greater than a thickness of the first case.

What is claimed is: 
     
         1 . A secondary battery comprising:
 an electrode assembly provided with a first electrode plate and a second electrode plate; and   a case in which the electrode assembly is accommodated,   wherein the case comprises:
 a first case having a recess, in which the electrode assembly is accommodated, at a central area thereof, wherein the first case has one opened surface; and 
 a second case configured to seal the one opened surface of the first case, 
 wherein the first case further comprises:
 an extension part extending from one end of the recess and coupled to the second case; and 
 a round part between the recess and the extension part, 
 wherein a curvature radius of the round part is equal to or greater than a thickness of the first case. 
 
   
     
     
         2 . The secondary battery as claimed in  claim 1 , wherein the curvature radius of the round part is approximately 100% to approximately 500% of the thickness of the first case. 
     
     
         3 . The secondary battery as claimed in  claim 1 , wherein the second case is a flat plate. 
     
     
         4 . The secondary battery as claimed in  claim 3 , wherein the extension part is parallel to the second case. 
     
     
         5 . The secondary battery as claimed in  claim 1 , wherein the case further comprises a coupling part coupling, by welding, the extension part of the first case to an edge of the second case. 
     
     
         6 . The secondary battery as claimed in  claim 5 , wherein the coupling part is provided by laser welding in a direction of the extension part of the first case from an outer surface of the second case and is adjacent to the recess. 
     
     
         7 . The secondary battery as claimed in  claim 5 , wherein the first case and the second case are sealed by the coupling part. 
     
     
         8 . The secondary battery as claimed in  claim 5 , wherein the coupling part is disposed at a boundary between the extension part of the first case and the round part. 
     
     
         9 . The secondary battery as claimed in  claim 1 , wherein each of the first case and the second case is made of steel, stainless steel, nickel-plated steel, or a steel alloy. 
     
     
         10 . The secondary battery as claimed in  claim 1 , wherein the recess has a rectangular parallelepiped shape with one surface opened, and wherein the extension part is bent to have a round part from four sides of one end of the recess so as to extend in a first direction parallel to the second case and a second direction. 
     
     
         11 . The secondary battery as claimed in  claim 1 , wherein each of the first case and the second case has a thickness of approximately 0.05 mm to approximately 0.4 mm. 
     
     
         12 . A method for manufacturing a secondary battery, the method comprising:
 welding a first case having a recess, in which an electrode assembly is accommodated, and an extension part extending to be bent outward from one end of the recess to a second case having a plate shape parallel to the first case to provide a coupling part through which the first case and the second case are coupled to each other by welding; and   removing an area, except for a first area on which the coupling part secures sealability of the first case and the second case, on the extension part of the first case and an edge area of the second case.   
     
     
         13 . The method as claimed in  claim 12 , wherein the recess has a rectangular parallelepiped shape with one opened surface, and
 the extension part is bent to have a round part from four sides of one end of the recess so as to extend in a first direction parallel to the second case and a second direction,   wherein a curvature radius of the round part is equal to or greater than a thickness of the first case.   
     
     
         14 . The method as claimed in  claim 13 , wherein the curvature radius of the round part is approximately 100% to approximately 500% of the thickness of the first case.